Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$201.31	5.665%	$212.7142	$212.71	$212.70	$212.70
Purchase #2	$34.73	11.294%	$38.6524	$38.65	$38.65	$38.70
Purchase #3	$42.25	6.460%	$44.9794	$44.98	$45.00	$45.00
Purchase #4	$127.96	12.431%	$143.8667	$143.87	$143.85	$143.90
Purchase #5	$63.86	12.273%	$71.6975	$71.70	$71.70	$71.70
Purchase #6	$74.44	10.653%	$82.3701	$82.37	$82.35	$82.40
Purchase #7	$37.64	6.494%	$40.0843	$40.08	$40.10	$40.10
7 purchase totals =	$582.19		$634.3646	$634.36	$634.35	$634.50